It is well-known in the art for vehicles to employ electronic devices to control the vehicle's ignition system. A typical production passenger vehicle often includes such a device which performs such a function along with other engine or vehicle control functions.
For instance, it is known to employ electronic devices that monitor the amount of acceleration or rotation of each individual wheel. When the tires are found not to be rotating in proper relative velocity or acceleration, the device directs power to be shifted from one wheel or axle to a different wheel or axle. Such a device is often referred to as a traction control device. Often, the improper relative velocity or acceleration among tires or axles is a likely indicator of a wheel slipping, a condition which causes a lack of control in operating the vehicle.
In addition, slippage prevents a vehicle from accelerating at maximum power. As is known, a static friction coefficient is higher than a sliding friction coefficient. When a wheel slips under power, the friction between the wheel and the roadway changes from static friction to sliding friction. Accordingly, the wheel begins to spin and slide against the road, and a portion of the acceleration power is lost.
In some instances, it is important to provide maximum power possible to a wheel under non-slip conditions. For example, when a vehicle is trying to climb a hill during adverse weather conditions, such as snow or other precipitation, it is critical that the vehicle not lose traction between the vehicle's tires and the surface of the road.
Another example is in racing, and, in particular, drag racing. Drag racing typically involves directing a vehicle down a generally straight track where a pair of cars race side-by-side, such as over a quarter-mile length. In the event the track conditions are less than ideal, the tires of the vehicle may start to slip if maximum power is delivered from the engine to the tires. A driver has to be able to sense slippage and back off from the accelerator. Once the tires have regained traction, the driver may then re-apply full acceleration.
The problem with relying on the driver is that the driver must first sense the slippage, and must be able to release the accelerator the proper amount for the proper time. Winning drag race times are measured in thousandths of a second, or less. The vehicles may travel a quarter mile in under eight seconds, and may reach speeds in the order of 300 mph. Therefore, a single slip condition may be the difference between winning or losing a race. It also should be recognized that, by mere luck, one driver in a two-vehicle race may draw an inferior track lane. Such a draw, alone, can determine winning and losing in drag racing.
However, the difficulty of reacting quickly to a slip condition that is presented to a driver in a drag race is not nearly as important as over-revving of the engine. In a typical drag race, the roadway is exposed to weather year round, can only be built within certain tolerances, and is, therefore, imperfect in and of itself. Some drag racing engines may rotate in the range of 12,500 revolutions per minute (RPM). When the vehicle's tires lose traction with the road, the lack of resistance frees the engine of the vehicle to excessively race or accelerate. Not only can this damage the engine and the vehicle, it can imperil the driver or bystanders if the engine should fail catastrophically, such as with an explosion.
In addition, engine over-revving may result from other factors than the described slip condition. Specifically, over-revving of the engine is, in many instances, due to a lack of resistance from the engine to the drive train. As stated, this may be because the tires have lost traction with the track surface. In addition, the lack of resistance may result from the engine becoming, in essence, disconnected from the drivetrain due to a slipping or blown clutch. A similar event occurs when the driver misses a gear and fails to re-engage the clutch before fully opening the throttle. Furthermore, the drivetrain itself may fail by having a component failure or the transmission blowing.
Accordingly, there has been a need for a device that minimizes the effects of slippage between a tire or wheel and a roadway or racetrack and that minimizes the likelihood of over-revving of an engine.